The goal of this clinical trial is to evaluate in real life, in patients with Hereditary Hemorrhagic Telangiectasia (HHT), the tolerance of the strategy of use of anticoagulant and/or antiplatelet, by comparing a new exposure period (first trimester of treatment) to a period of reference non-exposure (last trimester before start of treatment).

Currently there are no recommendations on the use of anticoagulant and/or antiplatelet treatment in patients with Rendu-Osler Disease.

The main question this study aims to answer is:

• to better determine which anticoagulant and/or antiplatelet therapy are best tolerated or if they are equivalent in Rendu-Osler disease because this type of treatment is often used in urgent and/or vital situations.

Participants will have a 2-year follow-up with biological monitoring of ferritin and hemoglobin level and ESS (Epistaxis Severity Score) and QoL-HHT (Quality of Life Hereditary Hemorrhagic Telangiectasia) questionnaires.

Inclusion Criteria:

• Patient with Rendu-Osler disease with an indication of antiplatelet and/or anticoagulant introduced for less than 3 months (inclusion period within 3 months of exposure)
• Age > 18 years old
• Patient able to understand and agree to participate in the study
• Affiliation to a social security system

Exclusion Criteria:

• Patient with an indication of antiplatelet and/or anticoagulant but for whom treatment has not been introduced or introduced for more than 3 months
• Refusal to participate
• Pregnant woman or who are breast feeding
• Patients under maintenance of justice, wardship or legal guardianship